The oil system on the Conquest engine is completely automatic which includes both a pressure and scavenge oil system.
The oil tank is mounted on the front lower portion of the engine and is serviced through an access panel mounted on the right hand side of the engine cowl when viewed from behind the engine.
|Oil tank position on the TPE331|
The oil system utilises one pressure pump and three scavenge pumps all of which are engine driven.
The pressure pump is required for the supply of high pressure oil to the engine for:
- The propeller for variable pitch control, and
- The torque meter for engine power measurement.
High pressure oil pump mounted on the top right of the engine
High pressure oil pump and filter assembly
Three scavenge pumps are used throughout the engine to aid in the movement of lubrication oil around the engine.
One scavenge pump moves oil from the rear turbine bearing directly to the reduction gearbox whilst the other two scavenge pumps move oil from the gearbox back to the oil tank ready for use again by the high pressure oil pump.
Low pressure oil scavenge pump positions.
During the engine start cycle an electrically controlled Oil Vent valve is used to reduce starter-generator drag by admitting air to the oil pumps.
The oil vent valve is opened automatically by pressing the engine start button and is closed either automatically by the computer during a normal mode start or manually by selection of a 60% switch during a manual mode start.
Oil vent valve used to reduce cranking effort required by the starter-generator during the start sequence.
A filter in the high pressure line removes solid particles from the oil during normal system operation. Should the filter become clogged, an oil filter bypass valve will open allowing an unfiltered flow of oil back to the system. Oil filter bypassing can be checked during the walk around by observation of the oil filter bypass button located above the oil filler cap.
|Oil bypass button will protrude if the filter has been bypassed. Check that it is flush prior to flight|
The oil system also utilises an oil cooler which is mounted on the lower rear section of the engine. A thermostatically controlled valve controls the amount of oil that flows through the oil cooler to maintain the oil temperature within defined limits.
Oil temperature and pressure are indicated to the pilot on a dual scale temperature/pressure guage located on the lower portion of the engine instrument cluster in the cockpit. An OIL PRESS warning light mounted on the annunciator panel wil also illuminate when the oil pressure drops below 40 PSI. Note: This warning light operates independantly of the oil pressure/temperature guage, therefore providing a means of checking a faulty oil pressure guage.
|Oil pressure/temp. guages
||Oil pressure warning light which illuminates below 40 PSI.
40 PSI switch mounted on the reduction gearbox housing
The Garrett TPE331 engine must be operated within the following limitations regarding the oil system:
- The oil system must be serviced only with the type and brand of oil currently used.
- DON’T MIX BRANDS OF LUBRICATING OIL.
- Do not operate the engine when the oil level is below the ADD mark on the dipstick.
- If the oil dipstick is abnormally low it is possible that the oil has been transferred to the reduction gearbox. If this is suspected motor the engine for 5-10 secs, then recheck the oil level.